Method for isolation of catmint oil

ABSTRACT

A high yielding method is described for improved isolation of catmint oil after recovery from catmint plants of the genus  Nepeta . Catmint oil can be obtained in quantitative yields for use in insect repellent compositions.

This application claims priority under 35 U.S.C. §119(e) from, andclaims the benefit of, U.S. application Ser. No. 13/509,061, filed May10, 2012, and U.S. Provisional Application No. 61/260,370, filed Nov.11, 2010.

TECHNICAL FIELD

This invention provides methods for improved recovery of catmint oilfrom plants of the genus Nepeta (catmint).

BACKGROUND

It has been demonstrated that dihydronepetalactone exhibits insectrepellency (see, for example, US 2005/0112166, which is by thisreference incorporated in its entirety as a part for all purposes).Dihydronepetalactone can be obtained by hydrogenation of nepetalactone,which may be isolated as a component of the essential oil of plants ofthe genus Nepeta (catmint plant). Essential oil from Nepeta plantmaterial, herein referred to as catmint oil, has been obtained byvarious isolation processes, including steam distillation, organicsolvent extraction, microwave-assisted organic solvent extraction,supercritical fluid extraction, mechanical extraction and enfleurage(initial cold extraction into fats followed by organic solventextraction). Steam distillation [such as described by Regnier, F. E. etal, Phytochemistry (1967) 6:1281-1289] is the most viable method forobtaining catmint oil. Disclosed in a commonly owned and co-pendingapplication published as US 2010/0034906 (which is by this referenceincorporated in its entirety as a part for all purposes) are improvedprocesses for steam distilling plant material from Nepeta cataria toobtain catmint oil.

For commercial production of the insect repellent dihydronepetalactoneas derived from catmint oil, it is desirable to have further increasedyields of catmint oil containing nepetalactone obtained from Nepetaplant material. A need thus remains for improved techniques for therecovery of catmint oil from Nepeta plants.

SUMMARY

The invention provides methods for recovering catmint oil that increasethe yield of catmint oil following steam extraction of catmint oilplants which are of the genus Nepeta.

In one embodiment, this invention provides a method for recoveringcatmint oil from plants of the genus Nepeta by (a) providing a firstliquid mixture comprising catmint oil and water; (b) contacting thefirst liquid mixture with at least one non-water miscible organicextracting solvent to form a second liquid mixture that contains asolvent phase and an aqueous phase; (c) in the second liquid mixture,separating the solvent phase from the aqueous phase, and recovering thesolvent phase; and (d) removing the extracting solvent from the solventphase to isolate the catmint oil.

In another embodiment, this invention provides a method for recoveringcatmint oil from plants of the genus Nepeta by (a) providing a firstliquid mixture comprising catmint oil and water; (b) in the first liquidmixture, separating catmint oil from water, and recovering the catmintoil; (c) contacting the catmint oil recovered in (b) with at least onenon-water miscible extracting solvent to form a second liquid mixturethat contains a solvent phase and an aqueous phase; (d) in the secondliquid mixture, separating the solvent phase from the aqueous phase, andrecovering the solvent phase; and (e) removing the extracting solventfrom the solvent phase to isolate the catmint oil.

In yet another embodiment, the combination of the catmint oil obtainedin steps (b) and (e) is the total isolated catmint oil.

DETAILED DESCRIPTION

This invention relates to improved methods for the recovery of catmintoil from plant material of the genus Nepeta. Catmint oil containsnepetalactone, and nepetalactone when hydrogenated yieldsdihydronepetalactone, which has been found to serve as an insectrepellent active. The term “insect repellent” or “insect repellentcomposition”, as used herein, refers to a compound or composition thatdeters insects from their preferred hosts or from articles ofmanufacture. Typically, an insect repellent is a compound or compositionthat can be either topically applied to a host, or incorporated into anarticle to deter insects from the space in which the host or articleexists.

The term “invention” as used herein is a non-limiting term, and is notintended to refer to any single embodiment of the various inventions tothe exclusion of others, but encompasses all possible embodiments asdescribed in the specification and the claims.

Where a range of numerical values is recited or established herein, therange includes the endpoints thereof and all the individual integers andfractions within the range, and also includes each of the narrowerranges therein formed by all the various possible combinations of thoseendpoints and internal integers and fractions to form subgroups of thelarger group of values within the stated range to the same extent as ifeach of those narrower ranges was explicitly recited. Where a range ofnumerical values is stated herein as being greater than a stated value,the range is nevertheless finite and is bounded on its upper end by avalue that is operable within the context of the invention as describedherein. Where a range of numerical values is stated herein as being lessthan a stated value, the range is nevertheless bounded on its lower endby a non-zero value.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, where an embodiment of thesubject matter is stated or described as comprising, including,containing, having, being composed of or being constituted by or ofcertain features or elements, one or more features or elements inaddition to those explicitly stated or described may be present in theembodiment. An alternative embodiment of the subject matter, however,may be stated or described as consisting essentially of certain featuresor elements, in which embodiment features or elements that wouldmaterially alter the principle of operation or the distinguishingcharacteristics of the embodiment are not present therein. A furtheralternative embodiment of the subject matter may be stated or describedas consisting of certain features or elements, in which embodiment, orin insubstantial variations thereof, only the features or elementsspecifically stated or described are present.

In this specification, unless explicitly stated otherwise or indicatedto the contrary by the context of usage, amounts, sizes, ranges,formulations, parameters, and other quantities and characteristicsrecited herein, particularly when modified by the term “about”, may butneed not be exact, and may also be approximate and/or larger or smaller(as desired) than stated, reflecting tolerances, conversion factors,rounding off, measurement error and the like, as well as the inclusionwithin a stated value of those values outside it that have, within thecontext of this invention, functional and/or operable equivalence to thestated value.

Improved Catmint Oil Extraction

Catmint oil exhibits several characteristics that lead to low recoveryof the oil from plant material using standard steam distillationtechniques commonly employed for the isolation of essential oils fromplant material. Catmint oil has a similar density to water, and does notreadily coalesce to form a separate oil phase from the condensed waterused in the steam distillation process. Additionally, nepetalactone, theprincipal constituent of catmint oil, hydrates at high temperatures tonon-volatile and unwanted side products. This invention overcomes thesedisadvantages of the isolation of catmint oil from plant material toprovide an enhanced method for recovering the oil in high yield atmoderate temperatures.

In the methods, the volatized mixture of catmint oil and water solutionresulting from steam distillation of Nepeta plant material (herein alsocalled catmint plant material) is contacted with a non-water miscibleorganic solvent that dissolves catmint oil. Applicants have found thatby using this extracting solvent, there is isolation of substantialamounts of catmint oil that remain in the aqueous portion of the steamdistillate when a catmint oil phase is separated without using theextracting solvent. Removal of the solvent under reduced pressureaffords catmint oil suitable for use in the preparation of hydrogenatedcatmint oil insect repellent. The yield of catmint oil may be improvedby at least about 50%, 55%, 60%, 65%, 70%, or greater to achieve overallquantitative yields of at least about 80%, 85%, 90%, 95%, or 99%. Forexample, the yield of catmint oil may, by a factor as set forth above,be greater than the yield of catmint oil obtained from the separation ofcatmint oil from water in the absence of an organic extracting solvent.The amount of improvement in recovery will vary depending on factorsincluding the level of recovery from steam distillation alone in aparticular process, the organic solvent used for further extraction, anduse of repetitions of an extraction process.

Steam Distillation

In the methods, catmint oil plants are subjected to steam distillationwith improved extraction following condensation of the resultingvolatized mixture of catmint oil and water. Any plants of the genusNepeta that contain nepetalactone in the catmint oil may be used.Preferred are plants of Nepeta cataria. Any method for steamdistillation of plant material that is known in the art may be used suchas that typically used for catmint oil recovery.

For example, according to conventional distillation processes forrecovering catmint oil, plant material from Nepeta cataria is contactedwith steam to form a vapor phase heterogeneous mixture comprisingpredominantly catmint oil and water. This volatized mixture is thencondensed to form a heterogeneous liquid mixture comprising catmint oiland water.

Diagrams of typical distillation apparatuses are shown in commonly ownedand co-pending application WO 2008/079261, which is by this referenceincorporated in its entirety as a part for all purposes. A traditionalsteam distillation apparatus may be used according to the followingdescription. Plant material is packed into a retort over a set of steaminjectors. A suitable retort that may be used for such purpose isavailable from Juniper Mfg. (Redmond, Oreg.). The lid of the retort isclosed and sealed to both the retort and to a condenser. Steam isinjected through the injection manifold (or steam injector) and into thepacked plant material. The steam provides two functions: 1) energy todisrupt the glandular (or secretory) trichomes on the plant and releasethe oil, and 2) formation of a heteroazeotrope with the oil whichvolatizes it sufficiently as to allow it to be transported into thevapor phase. The steam and volatized oil are condensed as a mixturedistillate.

Cooling water, from any suitable water source, flows through thecondenser. Its cooling effect allows the steam and catmint oil vapor tocondense. The condenser is configured in such a way as to allow gravityto drain the condensed water and catmint oil out of the condenser andinto a collection can. The water and catmint oil are ducted into thecollection can optionally using internal baffles in such a way as toproduce a quiescent zone to allow the oil and water to effectivelyseparate. The quiescent zone is the zone where the superficial velocityof the condensate is less than the disengagement velocity of the oilfrom the water. Typically, the temperature of the condensate iscontrolled at a modest temperature, approximately 40-60° C., to allowthe oil and water to effectively separate in the quiescent zone of theseparation can.

In known steam distillation processes for recovery of catmint oil, theseparated catmint oil and water form two phases with the catmint oilbeing the heavier, lower layer. The water is generally removed aswastewater, for example by decantation.

In addition, the steam distillation may be carried out in a distillationapparatus as described below. Plant material is packed into a retort.The lid of the retort is closed and sealed to both the retort and to acondenser. Steam for the distillation of the catmint plant material canbe provided by any suitable means such as by direct injection through aninjection manifold. In an alternative embodiment, the steam can beobtained by adding water to the retort, and boiling the water in thepresence of the plant material. The latter method is referred to asusing a direct fired retort. The steam and volatized catmint oil arecondensed, the catmint oil separated and collected as described above.

In one example of a steam extraction process, 13 kg of dried catmintplant material is packed into the retort above the steam injector sothat the retort is full, and the plant material is sealed securely tothe sides of the retort so that channeling of the steam along the insidewalls of the retort is minimized. The retort is sealed and made leaktight. Live steam produced in a separate boiler is injected into thebottom of the retort at a rate of 480 g/min for a total of 60 minutes.The pressure of the steam is slightly above atmospheric pressure toallow for pressure drop across the plant material and the condenser. Thecooling water flow is adjusted to the condenser so that the condensatetemperature is between about 45° C. and about 55° C. during thedistillation. It is desired to keep the temperature below about 75° C.,and preferably below about 60° C. or about 55° C. to reduce the tendencyfor the hydration of nepetalactone to occur. Rate of hydration tonepetalic acid, an undesirable by-product, increases with increasingtemperature. The temperature can be reduced by operating thedistillation apparatus under vacuum.

The amount of vacuum applied to the system will depend on the systemcomponents, however achieving an absolute pressure of about 13 kPa toabout 70 kPa is preferred. An absolute pressure of about 20 kPa to about45 kPa is more preferred. In addition, the application of vacuum can beused in systems where water is recycled from the collection can back tothe retort.

After the collection can is filled with condensate, the water phasecondensate is drawn from the collection can into a wastewater drain, orthe water is recycled.

The still is operated in this fashion for 1 hour. A total ofapproximately 2.2 kg of steam is used per kg of dried catmint plantmaterial. Approximately 50 mL or 52 grams of catmint oil is collected inthe bottom of the collection can. This corresponds to approximately 0.40wt % of the original dry weight of the catmint plant.

Enhanced Catmint Oil Recovery

In the methods, recovery of catmint oil from thevolatized-then-condensed mixture of catmint oil and water solution,obtained in a process as described above, is improved by enhancingseparation of a catmint oil-containing phase (solvent phase) and theaqueous phase of the distillate mixture. At least one extraction solventthat is a non-water miscible organic solvent that dissolves catmint oilremaining with the aqueous phase is added to the condensed mixture ofcatmint oil and water solution. Extraction solvents that may be used areany organic solvents that are non-water miscible, that dissolve catmintoil in an aqueous mixture, and that provide increased disengagement ofcatmint oil from the aqueous portion of the mixture. Such extractionsolvents will have a density that differs from water density in agreater amount than does the catmint oil density. Typically the densityof the extraction solvent differs from that of water by at least about0.1 g/cc. The difference may be either positive or negative.

Extraction solvents that may be used include without limitation hexanes,petroleum ether, toluene, xylenes, ethyl acetate, methyl acetate,dichloromethane (DCM) and chloroform. Due to the larger differences indensities and hydrophobicities of these solvents with respect to anaqueous solution, as compared to the density and hydrophobicity ofcatmint oil, the dissolved catmint oil in these solvents will moreeasily partition from the water in the condensed steam distillate into aseparate layer that can then be isolated from the aqueous layer.

Typically a single extraction solvent is used, although multiplesolvents may be used as mixtures or sequentially. Typically theextraction solvent is added to the condensed steam distillate and thecombination mixed then allowed to separate. Mixing may be by any methodsuch as by injection, stirring or shaking. Separation may be by anymethod such as settling or floating. Separation characteristics willdepend on the specific extraction solvent used. For example, when usinghexane as the extraction solvent, the separated hexane and catmint oilwill float on the aqueous portion of the mixture. When usingdichloromethane (DCM) as the extraction solvent, the separated DCM andcatmint oil will, by contrast, settle below the aqueous portion of themixture. Removal of the solvent under reduced pressure affords catmintoil suitable for use in the preparation of hydrogenated catmint oilinsect repellent.

The placement of a line that directs water from the collection can tothe retort will depend on the position of the water in the collectioncan, i.e. whether the water phase is on top of the catmint oil or belowthe catmint oil. Conventional collecting equipment may be used when theextraction solvent and catmint oil phase separates on top of the aqueoussolution. In addition, corrosion products that may be formed in thecondenser or collection can collect at the bottom of the collection can,contaminating the liquid phase that is at the bottom of the can.Therefore, an additional advantage to having the oil phase as the topphase is that it is separated from any corrosion products that may bepresent.

The extraction solvent and aqueous mixture may be collected into acollection can optionally using internal baffles in such a way as toproduce a quiescent zone to allow the extraction solvent containingcatmint oil phase and aqueous phase to effectively separate as describedabove for the original separation of catmint oil and aqueous mixture.

The extraction solvent containing catmint oil is isolated and theextraction solvent is removed by any suitable method known in the artsuch as by evaporation. The extracting solvent may be recovered andrecycled.

In an alternative embodiment, extracting solvent is added to the aqueousphase following separation of a catmint oil phase from aqueous phasefrom the condensed steam extraction mixture with no extracting solventadded. In this embodiment a portion of catmint oil is isolated withoutusing an extracting solvent, and an additional portion of catmint oil isrecovered using an extracting solvent.

In another embodiment extraction with the extracting solvent isperformed multiple times by addition to the initial condensed steamextraction mixture, and/or to the initial separated aqueous phase, andto subsequent separated aqueous phases. Extractions may be performeduntil at least about 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%,or 99% of catmint oil in the condensed steam distillate from catmint oilplant material is recovered.

Application of Catmint Oil

Recovered catmint oil may be used to prepare an insect repellentcomposition. The catmint oil is hydrogenated to convert thenepetalactone into dihydronepetalactone, which is an effective insectrepellent. Nepetalactone, which naturally occurs in differentstereoisomers in catmint oil, is hydrogenated to form mixtures ofdihydronepetalactone stereoisomers, or dihydronepetalactones. Oneexample of hydrogenation to produce dihydronepetalactones usingcatalysts such as palladium, or carbon and palladium, supported onstrontium carbonate is described in Regnier et al [Phytochemistry6:1281-1289 (1967)].

For example, the hydrogenation reaction may be carried out in thepresence of hydrogen at a temperature of about −10° C. to about 200° C.The hydrogen pressure for the reaction is generally from about 0.1 MPato about 20.7 MPa. The time, temperature, hydrogen pressure and flowrate and feed may be adjusted, according to known principles, to obtainoptimal conversion of hydrogenation of catmint oil using a givencatalyst. A suitable hydrogenation reaction is that which is describedin U.S. Pat. No. 7,067,677 (which is by this reference incorporated inits entirety as a part for all purposes). Described therein is thehydrogenation of nepetalactone in the presence of a catalytic metal thatis not nickel, platinum or palladium. The process can be carried out ata temperature of about 25° C. to about 250° C. at a hydrogen pressure ofabout 0.1 MPa to about 20 MPa. Other suitable processes for making adihydronepetalactone include a process as described in the commonlyowned and co-pending application published in U.S. 2010/0168447, whichis by this reference incorporated in its entirety as a part for allpurposes. A hydrogenation reaction may be carried out in batch in asingle reactor, in sequential batch in a series of reactors, in reactionzones within one or more reactors, or in continuous mode in any of theequipment customarily employed for continuous processes.

Hydrogenated catmint oil is incorporated into formulations suitable forapplication to the skin, hair, fur, feathers or hide of a human ordomesticated animal. In addition, insect repellent formulations may beapplied to, or incorporated into articles. Insect repellent formulationsare designed to provide a minimum effective evaporation rate from theskin surface or insect repellent article to maintain the necessaryminimum concentration of repellent in the air space directly above theskin surface/article for effective insect repellency. Disclosed incommonly owned and co-pending applications published, respectively, asUS 2005/112166 and US 2007/0264297 (each of which is by this referenceincorporated in its entirety as a part for all purposes) are effectivecarriers and insect repellent compositions prepared using catmint oil.

Insect repellent compositions containing dihydronepetalactones areeffective against a variety of insects which interfere with humansociety including a variety of biting insects (ants, bees, black flies,chiggers, fleas, mosquitoes, stable flies, ticks, wasps), wood-boringinsects (termites), noxious insects (house flies, cockroaches, lice,wood lice), and household pests (flour and bean beetles, dust mites,moths, silver-fish, weevils).

EXAMPLES

The operation and effects of certain embodiments of the inventions maybe more fully appreciated from a series of examples (Examples 1-2), asdescribed below. The embodiments on which these examples are based arerepresentative only, and the selection of those embodiments toillustrate the invention does not indicate that materials, components,reactants, conditions, steps or techniques not described in the examplesare not suitable for use herein, or that subject matter not described inthe examples is excluded from the scope of the appended claims andequivalents thereof.

The following abbreviations are used: ° C. is degrees Centigrade; Kg iskilogram; g is gram; min is minute; ml is milliliter(s); CMO is catmintoil.

Example 1 Extraction of Catmint Oil from CMO/Water Mixture withDichloromethane

Catmint oil (purchased from Thacker brothers, 1.73 g) was added to aseparatory funnel followed by addition of 100 g of water. The mixture(approximately 1.73% weight/weight) was stirred, and the catmint oil(CMO) layer, which is slightly heavier than water, was allowed tosettle. The CMO layer was then separated from the water layer in aseparatory funnel and weighed. This recovered CMO was called the firstamount of CMO.

Droplets of CMO remaining in the water layer were visible indicatingthat the CMO did not fully separate from the water. A volume of 20 mldichloromethane (DCM), a solvent heavier than water, was then added tothe separatory funnel containing rest of the CMO/water mixture. Thefunnel was shaken. Droplets of CMO disappeared when DCM was added, andthe CMO/water mixture was shaken indicating that the CMO partitionedinto the DCM fraction. The DCM, including partitioned CMO, was allowedto settle and then was isolated from the separatory funnel. A total ofthree extractions were performed using 20 ml DCM each time, and thethree CMO/DCM mixtures were combined. The combined CMO/DCM mixtures weredried over sodium sulfate, and DCM was removed under reduced pressure ona rotary evaporator. The resulting sample, which was the second amountof CMO, was weighed. Together the first and second amounts of CMO gavethe total CMO yield. Total percent CMO yield was calculated by dividingthe total weight of CMO recovered in grams as a fraction of starting CMOamount (1.73 g). Results are given in Table 1 below.

Example 2 Extraction of Catmint Oil from CMO/Water Mixture with Hexane

Catmint oil (purchased from Thacker brothers, 1.56 g) was added to aseparating funnel followed by addition of 150 g of water. The mixture(approximately 1.04% weight/weight) was stirred, and the catmint oil(CMO) layer, which is slightly heavier than water, was allowed tosettle. The CMO layer was then separated from the water layer andweighed. This recovered CMO was called the first amount of CMO.

Droplets of CMO remaining in the water layer were visible indicatingthat the CMO did not fully separate from the water. A volume of 20 mlhexane (HXN), a solvent lighter than water, was then added to theseparatory funnel containing the rest of the CMO/water mixture. Thefunnel was shaken. Droplets of CMO disappeared when HXN was added, andthe CMO/water mixture was shaken indicating that the CMO partitionedinto the HXN fraction. The HXN, including partitioned CMO, was allowedto float and then was isolated from the separatory funnel. A total ofthree extractions were performed using 20 ml HXN each time, and thethree CMO/HXN mixtures were combined. The combined CMO/HXN mixtures weredried over sodium sulfate, and HXN was removed under reduced pressure ona rotary evaporator. The resulting sample, which was the second amountof CMO, was weighed. Together the first and second amounts of CMO gavethe total CMO yield. Total percent CMO yield was calculated by dividingthe total weight of CMO recovered in grams as a fraction of starting CMOamount (1.56 g). Results are given in Table 1.

TABLE 1 Recovery of CMO from water. Start- First Second Start- ingamount % amount Total Total ing CMO of CMO of CMO % CMO Water Sol- % inCMO re- CMO yield CMO (g) (g) vent water (g) covered (g) (g) yield 1.73100 DCM 1.73% 0.45 26.01% 1.27 1.72 99.42% 1.56 150 HXN 1.04% 0.3421.79% 0.97 1.31 83.97%

In other embodiments, the methods could be conducted as described below.Steam distillation of catmint oil is carried out in a distillationapparatus consisting of a retort, steam generator, condenser andreceiver to capture the condensate. Dried catmint plant material ispacked into the retort of the distillation apparatus so that the retortis full. The retort is sealed, and steam is injected into the bottom ofthe retort. The pressure of the steam is slightly above atmosphericpressure, and the cooling water temperature in the condenser of thedistillation apparatus is adjusted so that the condensate temperature inthe receiver is between 45° C. and 55° C. during the distillation.

After the distillation is complete, the collected condensate in thereceiver mixture consisting of catmint oil and water is transferred to aseparatory funnel. A water immiscible extraction solvent, such ashexane, is added and the mixture is shaken in order to thoroughly mixthe water and solvent layers. The mixture is allowed to stand in orderfor the layers to completely separate into two distinct liquid phases.The water layer is separated from the extraction solvent layer. Theextraction solvent is evaporated from the solvent layer for recovery ofthe catmint oil.

Thus, catmint oil can be isolated after recovery from plants of thegenus Nepeta by a method comprising:

-   -   (a) providing a first liquid mixture comprising catmint oil and        water;    -   (b) contacting the first liquid mixture with at least one        non-water miscible organic extracting solvent to form a second        liquid mixture;    -   (c) separating from an aqueous phase in the second liquid        mixture a solvent phase that comprises catmint oil and the        extracting solvent; and    -   (d) removing the extracting solvent from the solvent phase to        isolate catmint oil.

Alternatively, catmint oil can be isolated after recovery from plants ofthe genus Nepeta by a method comprising:

-   -   (a) providing a first liquid mixture comprising catmint oil and        water;    -   (b) separating catmint oil from an aqueous phase in the first        liquid mixture;    -   (c) contacting the aqueous phase with at least one non-water        miscible extracting solvent to form a second liquid mixture;    -   (d) separating from an aqueous phase in the second liquid        mixture a solvent phase that comprises catmint oil and the        extracting solvent; and    -   (e) removing the extracting solvent from the solvent phase to        isolate catmint oil.

What is claimed is:
 1. A method for recovering catmint oil from plantsof the genus Nepeta, comprising (a) providing a first liquid mixturecomprising catmint oil and water; (b) contacting the first liquidmixture with at least one water-immiscible organic extracting solvent toform a second liquid mixture that contains a solvent phase and anaqueous phase; (c) in the second liquid mixture, separating the solventphase from the aqueous phase, and recovering the solvent phase; and (d)removing the extracting solvent from the solvent phase to isolate thecatmint oil.
 2. A method for recovering catmint oil from plants of thegenus Nepeta, comprising (a) providing a first liquid mixture comprisingcatmint oil and water; (b) in the first liquid mixture, separatingcatmint oil from water, and recovering the catmint oil; (c) contactingthe catmint oil recovered in (b) with at least one water-immiscibleextracting solvent to form a second liquid mixture that contains asolvent phase and an aqueous phase; (d) in the second liquid mixture,separating the solvent phase from the aqueous phase, and recovering thesolvent phase; and (e) removing the extracting solvent from the solventphase to isolate the catmint oil.
 3. A method according to claim 1 or 2wherein an aqueous phase from which a catmint oil phase has beenseparated is contacted with at least one water-immiscible extractingsolvent, and a catmint oil and extracting solvent phase is separated,the extracting solvent removed, and the catmint oil recovered.
 4. Amethod according to claim 1 or 2 wherein the yield of catmint oil is atleast about 50% greater than the yield of catmint oil obtained from theseparation of catmint oil from water in the absence of an organicextracting solvent.
 5. A method according to claim 1 or 2 wherein thewater immiscible organic extracting solvent has a density that isdifferent from the density of water by at least about 0.1 Wm.
 6. Amethod according to claim 5 wherein the water immiscible organicextracting solvent is selected from the group consisting of a hexane,petroleum ether, toluene, a xylene, ethyl acetate, dichloromethane(DCM), chloroform and mixtures thereof.
 7. A method according to claim 1or 2 further comprising hydrogenating the recovered catmint oil.
 8. Amethod according to claim 7 further comprising formulating thehydrogenated catmint oil in an insect repellent composition.